Temperature and pressure responsive electric switch



Jan. 27, .1959

'r. J. \SULLIVAN TEMPERATURE AND PRESSURE RESPONSIVE ELECTRIC SWITCH Filed Sept. 27, 1957 2 I1 1 El i 42. 511111.1

2 Sheets-Sheet 1 I ATTORNEYS Jan. 27, 1959 "r. J. S'VULLIVAN 2,871,317

TEMPERATURE AND PRESSURE RESPONSIVE ELECTRIC SWITCH Filed Sept. 27, 1957 2 Sheets-Sheet 2 H 2 z w w *3 M W H N M h a V is} W 5 5"" g t q I I Q 5, 1 5: 6 m w a w IIIllllllIllIIIIIIIIIIIIIIIIIIIIIIIIIII g INVENTOR ATTORNEYS United States Patent 2,871,317 TEMPERATURE AND PRESSURE RESPONSIVE ELECTRIC SWITCH Timothy J. Sullivan, Butte, Mont, assignor to Sullivan Valve and Engineering Company, Butte, Mont, a corporation of Montana Application September 27, 1957, Serial No. 686,736 Claims. (Cl. 209-440) The present invention relates generally to an electric switch, and more particularly to an electric switch which is responsive to both temperaturue and pressure.

In many commercial and residential installations it is desirable to provide an electric switch which will open an electrical circuit when either the temperature or pressure of certain equipment exceeds predetermined values. The present invention relates to a temperature and pressure responsive switch particularly adapted for use with pressure vessels such as boilers, furnaces, ovens, refineries and the like.

The primary object of my invention is to provide an electric switch which will automatically open an electrical circuit when either the temperature or pressure of associated equipment exceeds certain predetermined values.

A more specific object of my invention is to provide an electrical switch having a movable contact held into engagement with a stationary contact by means of a retaining member the position of which is controlled by both a fusible link element and a pressure-responsive bellows element.

Still another object of my invention is to provide an electrical switch responsive to the internal temperatures and pressures within a pressure vessel, which switch may be removed from the vessel without enabling dis charge of fluids contained therein.

Other objects and advantages of my invention will become more apparent from a study of the following specification when considered in conjunction with the accompanying drawings in which:

Fig. l is a partly sectioned longitudinal elevational View of my switch actuator;

Fig. 2 is a partly sectioned plan view of the device taken along line 22 of Fig. 1; and

Fig. 3 is a partially cut-away end elevation of the switch.

Referring now more particularly to the drawings, switch unit 1 is rigidly connected to the metal housing 2 by means of screws 3 and contains a stationary electrical contact 4 and a movable contact 5 pivotally mounted upon fixed pivot 6. Internal leads 4, 5' connect the contacts to terminal connectors '7 and which are in turn connected to conductors 9 and it) of the power cable 11. Compressed coil spring 112 secured within the switch 1 tends to bias movable contact 5 out of on gagement with stationary contact 4-.

Slidably movable in bearing member 12 secured in opening 13 of the switch housing 2 is the switch actuating rod 14 having a cylindrical retaining or head member 15 threadably connected at one end thereof adjacent the switch unit 1. The retaining member 15 is of an electrical insulating material such as rubber, polyethylene or the like and is so arranged with respect to the switch unit 1 that the periphery of the member 15 engages projecting portion 5a of the movable contact 5 to retain the contact into engagement with stationary contact 4 against the biasing action of coil spring 112 (Fig. 3).

Compressed coil spring 30 positioned intermediate the head member 15 and bearing 12 tends to bias rod member 15 from movable contact 5.

2,811,317 Patented Jan. 27, 1959 14 to the left in Fig. 1 to displace member 15 from projecting portion 5a of the movable contact 5' as will be explained in greater detail below.

Removably secured at one end by screws 2 to the switch housing 2 concentrically about the rod 14 is metal sleeve 16. Screw-threadably connected to the other end of the sleeve 16 is a metal tubular member 17 having flexible bellows 18 secured thereto. The bellows 13 is preferably formed of a heat resistive metal, such as copper or the like, but it is of course possible to make the bellows from rubber, leather, plastic or any other suitable material.

Screw-threadably connected within the bore of the tubular member 17 is a transverse pin 19 having a bore 19a therethrough in which is slidably mounted trip rod 20. One end of trip rod 20 is formed into an enlarged portion 211a adapted to cooperate with the vertical portion 18a of the bellows 18. The other end of the trip rod 20 is connected to the trip actuating cylinder 21 which is slidably movable axially within the sleeve 16. Compression coil spring 22 positioned about trip rod 20 intermediate plug 19 and enlarged portion 20a serves to move rod 20 to the right in Fig. i so that the cylinder 21 will come into contact with the edge 17:: of tubular member 17 and to cause the bellows 18 to be expanded by the enlarged portion 20:: of trip rod 251.

Secured to the bearing 12 within the sleeve 16 is an elongated U-shaped metal support rod 23 (Fig. 2) having a trip lever 24 pivotally connected to the transverse portion 23a thereof. Removably connected at one end to the depending projection 24a of trip lever 24 and at the other end to hooked portion 14a of actuating rod 14 is a temperature-responsive fusible link element 25. Fusible link element 25 serves to maintain actuating rod 14 in its right-hand retracted position shown in Fig. 2 against the compressed tension of coil spring 3%.

Slidably mounted upon the outer periphery of sleeve 16 is an externally-threaded tubular element 27 adapted to be threadably connected to an opening in support 28, which may be the structural wall of a boiler, furnace or the like. If desired, O-ring 29 may be provided intermediate sleeve 16 and tubuluar member 27 to provide a seal between the fiuids on either side of the support 28.

The operation of the switch may now be readily described.

The sleeve 16 of the device is inserted through the opening in the container wall 23 and the tubular member 27 is threadably connected thereto so that the bellows 18 and the temperature-responsive fusible link 25 extend within the chamber the temperature and pres sure of which are to be controlled. Fusible link 25 is connected at one end to the trip lever 2% and at the other end to the hook portion 14:1 of ctuating rod 1 so that rod 14 is in the retracted position of Fig. l, with retaining member 15 in engagement with movable contact 5 to effect electrical contact between contacts 4 and 5. The conductors 9 and 10 are then connected in series with the power supply circuit of the associated electrical equipment which is to be controlled.

Upon the'building up of pressure in the vessel above a desired predetermined level, bellows will be caused to contract against the tension of spring 22 so that trip rod 20 will move to the left in Fig. 1 to cause head member 21 secured thereto to engage projection 24b and effect clockwise pivotal rotation of trip lever 24 about the U-shaped rod transverse portion 230. The projection 24a will thus be pivotally removed from fusible link 25 so that actuating rod 14 is free to be moved axially to the left in Fig. 1 by spring 3% to displace Spring 112 will then expand to cause movable contact 5 to pivot out of electrical contact with stationary contact 4 and thus break the electrical connection between conductors 9 and 10. f

When the switchis in the presetcondition of Fig. 1, upon an increase in temperature in the vessel or chamber above a predetermined value, the fusible link element 25 will break to release the hook 14a and permit rod 14 to move to the left in Fig. 1 under the biasing action of spring 30 to cause axial displacement of head 15 and opening of the switch as described above.

In order to reset the switch after the fusible link has been broken upon excessive temperature, the screws 2 are removed so that the switch housing 2 will be disconnected from the sleeve 16. Bearing 12, actuating rod 14, and the U-shaped rod 23 are then removed as a unit with the switch housing. Sleeve 16 will be retained in the tubular member 27 in the support 28 and no fluid will escape from the container in view of the sealing of the sleeve at one end by the bellows 18 and in view of the seal provided by the O-ring 29. The broken parts of the fusible link are then removed and a new link is connected at one end to the projection 24a of trip lever 24 and at the other end to hook portion 14a of rod 14 so that head member 15 will come into engagement with movable contact to cause the movable contact to engage stationary contact 4 to close the switch circuit. The U-shaped rod 23 supporting the fusible link 25 is then inserted into the sleeve 16 and the housing 2 is again connected to flange 16a by screws 2'.

Thus it is apparent that the electrical switch of my invention is readily responsive to changes in temperature or pressure above predetermined values and also the structure of the switch is such as to allow simple resetting of the device after disconnection without any escape of fluid from the receptacle to which the switch is secured.

While in accordance with the patent statutes I have illustrated and described the best form of embodiment of my invention now known to me, it will be apparent to others skilled in the art that certain changes and modifications may be made in the device without deviating from the spirit of my invention as set forth in the appended claims:

I claim:

1. A temperature and pressure responsive electric switch comprising a housing; a switch unit secured within said housing and having a stationary contact, a movable contact adapted to contact said stationary-contact, and spring means biasing said movable contact out of engagement with said stationary contact; a retaining member slidably mounted in one wall of said housing adjacent said switch unit for normally maintaining said movable contact in electrical contact with said stationary contact; spring means biasing said retaining member out of engagement with said movable contact; means including a rigid fusible link and a latch trip for normally connecting said retaining member to said housing in opposition to said retaining member spring biasing means; and pressure-responsive bellows means connected to said housing adjacent said latch trip to actuate said trip and release said retaining member upon the presence of pressure above a predetermined value.

2. An electric switch as defined in claim 1 wherein said fusible link and said pressure-responsive bellows means are mounted externally of said switch housing.

3. An electric switch responsive to the temperature and pressure within a receptacle comprising a sleeve extending through and secured within an opening in the wall of the receptacle; a flexible bellows member secured to the end of said sleeve within the receptacle and closing said sleeve end; a trip actuating member connected to said bellows and longitudinally movable in said sleeve; a housing removably secured to the other end of said sleeve outside the receptacle; a switch unit secured within said housing and having a stationary contact, a movable contact, and spring means biasing said movable contact out of engagement with said stationary contact; a retaining member slidably niounted in one wall of said housing adjacent said switch unit, said retaining member having a head portion at one end thereof within said housing for normally maintaining said movable contact in electrical contact with said stationary contact and a hook portion at the other end thereof extending within said sleeve; a rigid support member within said sleeve, one end of said support member being connected to said housing and the other end of said support memher having a latch secured thereto adjacent said trip actuating member; a spring member positioned about said retaining member intermediate said head portion and said housing for biasing said retaining member out of engagement with said movable contact; and a temperature-responsive fusible link element removably secured at one end to said retaining member hook portion and at the other end to said latch to normally retain said head portion in engagement with said movable contact against the biasing action of retaining member biasing spring to effect electrical contact between said movable contact and said stationary contact, whereby upon the presence of temperature above a predetermined value said fusible link will break to release said retaining member so that said switch contacts will be opened.

4. An actuator responsive to the pressure and temperature within a closed vessel comprising a rigid sleeve extending through and secured within an opening in the wall of the vessel; a flexible pressure-responsive bellows element secured to the end of said sleeve within the vessel and closing said sleeve end in a fluid-tight manner; a bearing member removably secured to the other end of said sleeve external of the vessel; an output shaft slidably mounted in said bearing member for longitudinal displacement with respect thereto, one end of said shaft terminating within said sleeve member; spring means biasing said output shaft longitudinally in a direction away from sad bellows member; a rigid supporting member within said sleeve, one end of said supporting member being connected to said removable bearing member and the other end of said supporting member terminating adjacent said bellows element; latch means secured to said end of the supporting member terminating adjacent said bellows element; a rigid temperatureresponsive fusible link mounted entirely within said sleeve and extending within that portion thereof which extends into the pressure vessel, one end of said fusible link being removably connected to said latch means and the other end of said fusible link being removably connected to the end of said output shaft terminating within said sleeve, said fusible link serving to retain said output shaft in a retracted position against the biasing force of said spring means; and latch tripping means connected to said bellows and longitudinally movable in said sleeve adjacent said latch member, said tripping means being movable by said bellows upon the presence of pressure in the vessel above a predetermined desired value to trip the latch member and to release the output shaft for longitudinal displacement by said spring biasing means.

5. A temperature and pressure responsive actuator as defined in claim 4 wherein said supporting member comprises a U-shaped rod, the extremities of the legs of said rod being removably connected to said bearing member, said latch means being secured to the transverse portion of said rod.

References Cited in the file of this patent UNITED STATES PATENTS 2,268,633 Aske Jan. 6, 1942 2,351,068 Wells June 13, 1944 2,351,408 De Beaumont June 13, 1944 2,454,288 Michaelson Nov. 23, 1948 

